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Turbulent flow over superhydrophobic surfaces with streamwise grooves

Türk, S.; Daschiel, G.; Stroh, A.; Hasegawa, Y.; Frohnapfel, B.

We investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. ... mehr

DOI: 10.1017/jfm.2014.137
Zitationen: 55
Web of Science
Zitationen: 53
Zitationen: 54
Zugehörige Institution(en) am KIT Institut für Strömungsmechanik (ISTM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2014
Sprache Englisch
Identifikator ISSN: 0022-1120
KITopen-ID: 1000047787
Erschienen in Journal of Fluid Mechanics
Verlag Cambridge University Press (CUP)
Band 747
Heft 1
Seiten 186-217
Nachgewiesen in Scopus
Web of Science
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